1. Field of the Invention
This invention relates to surgical cutting instruments. More particularly, this invention relates to novel surgical cutting heads or tips for performing surgery on various parts of the body, such as menisci (fibrous cartilages) located in body joints, e.g., knees, elbows and shoulders, or to remove malignant or non-malignant fibroids or similar tissues through small incisions in various parts of the body, and especially for use in infusion/aspiration devices for surgically removing cataractous tissue from the eye. The surgical cutting instruments of this invention will be described herein with reference in particular to cataract surgery.
2. Description of the Related Art
The eye's lens, a tough, almost completely transparent biconvex structure suspended behind the iris, is made up of an elastic capsule filled with cellular tissue. The lens is susceptible to cataract formation--changes in the lens which make it opaque and which may hinder or destroy vision depending on the size, shape and location of the cataract. Cataracts can be congenital. They can also be caused by degenerative changes in the lens with age (senile cataracts). Cataracts can also result from trauma, or from overexposure of the eye to heat, X-rays, ultraviolet rays or radioactive materials, or as a secondary effect of intraocular or systemic diseases, such as diabetes, or from exposure to various drugs. Cataracts can be cortical, involving largely or exclusively changes in the outer portion of the lens, or dense nuclear, involving primarily changes deep in the interior of the lens, or can involve most if not all of the proteinaceous material of the lens.
Treatment for cataracts generally involves removal of all or part of the lens through a small surgical incision (generally of about 3 mm to about 9 mm in length) made in the limbus, the portion of the sclera adjacent the cornea. Typically the lens is replaced with a synthetic intraocular lens material, or a contact lens or a thick eyeglass is used to function as did the lens. Intracapsular cataract extraction ("ICCE") involves removal of the lens and the entire capsule. This technique is no longer in common use, except for subluxated lens and ocular trauma where the capsule or zonules are badly damaged. When extracapsular cataract extraction ("ECCE") is performed, a 4 to 7 mm portion of the anterior capsule and the nucleus of the lens are removed, leaving the posterior capsule behind.
The main thrust of more modern cataract surgery has been towards smaller limbal incisions and less invasive approaches. Indeed, the success of the newest techniques now being developed to preserve and restore accommodation (the ability to focus properly), such as refilling the entire lens with a synthetic substance once the cataractous material has been removed, will depend upon the development of new instruments that can remove cataractous materials, including cataractous nuclei, through the smallest possible hole made at the periphery of the lens capsule. It is an object of the present invention to provide such instruments.